Retrofit Is In

It’s easy to talk about building new houses that are energy efficient. When you build from the ground up, you can do anything—the thickest insulation, the best sealants, the most efficient furnace; but what about older houses? Is it possible to take a house built 100 years ago—when insulation, if it existed at all, consisted of wadded-up newspapers—and make it as energy efficient as a brand-new dwelling?